Over fifty thousand cases of transitional cell carcinoma (TCC) of the bladder are diagnosed in the United States yearly. Most patients initially present with superficial bladder TCC and those with high grade TCC eventually recur or progress. The preliminary and proposed studies are based on the hypothesis that adenovirus vector-mediated gene transfer of apoptosis-inducing genes is a rational alternative for intravesical TCC therapy. WE evaluated basal expression of BCL-X/L (an inhibitor of apoptosis) in human TCC. Immunohistochemistry showed Bcl-X protein over-expression in malignant compared to normal transitional epithelium. Western blot determined that this protein was Bcl-X/L and that Bcl-X/S, was not detectable in malignant or normal transitional epithelium. This provided rationale for evaluating the ability of Ad- bcl-x/S (an adenoviral vector carrying the Bclx-S gene) to induce apoptosis in TCC. The receptivity of transitional epithelium for gene transfer by adenoviral vectors in vivo was demonstrated by detecting lacZ expression after intravesical instillation of Ad-lacZ (an adenoviral vector carrying the lacZ reporter gene). Vector dose- dependent apoptosis was specifically induced after infection of TCC by Ad-bcl-X/S in vitro. Analysis of T cell proliferation after administration of Ad-bcl-X/S showed that the presence of bcl-X/S does not abrogate vector-specific immunity. Based on these preliminary findings, this project will address three specific aims: 1) To determine the effects of Ad-bcl-X/S and Ad-hrk on apoptosis in normal versus cancerous transitional epithelium in vivo. Gene transfer efficiency, apoptosis induction, and tumor progression in vivo and toxicity will be measured after intravesical administration of Ad-bcl-X/S Ad-hrk or AdlacZ in rodent models of TCC. 2) To evaluate resistance mechanism to apoptosis-inducing adenovirus vector efficacy. Effects of Bcl-X/L expression and p53 status on apoptosis induction will be evaluated as possible resistance mechanisms to Ad-bcl-X/S gene therapy. 3) To characterize the immune response to regionally administered , apoptosis- inducing, adenovirus vectors. Effects of presenting cell apoptosis on vector-specific T cell and neutralizing antibody induction and the interaction of tumor-specific and vector-specific immunity will be evaluated. These studies will serve to guide design of clinical trials evaluating the safety and efficacy of apoptosis-inducing adenovirus vectors as intravesical therapy for TCC.